Add waiting time before loading autocomplete information

[Bertware]

Prevent querying the stations list too much. The limit is 2 requests per second, with an additional burst of 6. Passing this limit will cause 503 responses and the auto-complete list will temporary disappear.

Proposed solution:
The station name auto-complete should wait 300ms before searching. If in this period, another character is typed, the interval should be reset. Once the interval has elapsed, the text which is then typed should be searched.